buffet: Pass --enable_xmpp flag through init script

BUG=brillo:769
TEST=Running buffet_Registration against buffet with this code
     yields log messages about XMPP being disabled by flag.

Change-Id: I21e618025e2f79a8557780db4d30ed3d5818dd37
Reviewed-on: https://chromium-review.googlesource.com/265761
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/etc/init/buffet.conf b/buffet/etc/init/buffet.conf
index 49c7b7f..ba4adb2 100644
--- a/buffet/etc/init/buffet.conf
+++ b/buffet/etc/init/buffet.conf
@@ -10,6 +10,7 @@
 respawn
 
 env BUFFET_LOG_LEVEL=0
+env BUFFET_ENABLE_XMPP=
 env BUFFET_STATE_PATH=
 env BUFFET_CONFIG_PATH=
 env BUFFET_TEST_DEFINITIONS_PATH=
@@ -26,7 +27,8 @@
     --v="${BUFFET_LOG_LEVEL}" \
     --config_path="${BUFFET_CONFIG_PATH}" \
     --state_path="${BUFFET_STATE_PATH}" \
-    --test_definitions_path="${BUFFET_TEST_DEFINITIONS_PATH}"
+    --test_definitions_path="${BUFFET_TEST_DEFINITIONS_PATH}" \
+    --enable_xmpp="${BUFFET_ENABLE_XMPP}"
 
 # Wait for daemon to claim its D-Bus name before transitioning to started.
 post-start exec gdbus wait --system --timeout 30 org.chromium.Buffet